Control system for audio-visual devices connected by cables

ABSTRACT

A system for controlling any of a plurality of information storage or generating devices which are grouped in operative association with common connectors along a cable common thereto by any of a plurality of remote stations which are also grouped in operative association with common connectors along a common cable. Means are provided for generating from a station a signal representative of a device address to transfer such signal to each of the devices. Means are provided for comparing the generated signal with device addresses registered in association with the devices whereby, upon identity therebetween, control of the device is effected to the generating station first to request such control. Feedback means are provided operative with the generating station and other stations to indicate the status of the device and its function, and to indicate when control thereof has been relinquished. Means enabling an overriding control station are also provided.

United States Patent Calvagna et al.

[54] CONTROL SYSTEM FOR AUDIO- VISUAL DEVICES CONNECTED BY 3/1970Belcher ..340/1 52 X CABLES Primary Examiner-Harold l. Pitts [72]lnvemors James F Calvaana Anaheim Roger Attomey-Nilsson, Robbins, Wills&Berliner Q S i A. Bailing, Santa Ana, both of Calif. 57 ABSTRACT [73]Asslgnee: Community Bank Downey Cahf' A system for controlling any of aplurality of informa- [22] Filed; April 15, 1970 tion storage orgenerating devices which are grouped in operative association withcommon connectors [21] Appl' along a cable common thereto by any of aplurality of remote stations which are also grouped in operative 52 US.(:1. .340/152 n, 340/147 LP asmiation with common connecwrs alone acommon 51 Int. 01. ..H04q 3/00, H04q 5/00 cable- Means are Provided forgenerating from a [58] Field of starch ..34o/1s2 R 147 LP a signalrepresentative a device address m transfer such signal to each of thedevices. Means are [56] References Cited provided for comparing thegenerated signal with device addresses registered in association withthe UNITED STATES PATENTS devices whereby, upon identity therebetween,control of the device is effected to the generating station first torequest such control. Feedback means are provided 50374 9 1964 operativewith the generating station and other stal 66 gunstem "340/147 c tionsto indicate the status of the device and its func- ,2 ,553 ya C tion andto indicate when control thereof has been relinquished. Means enablingan. overriding control tat a1 d d- 3,253,263 5/1966 Lee ..340/152 x Sare e 3,274,554 9/1966 Hopper ..340/l52 X 20 Claims, 13 Drawing FiguresREMOTE REMOTE 5 TQT/ ON MO/V/ TOR 5 71 77 ON F' 'E B E I p4, TERM/NA'LSK7 2/ 15 11 29 E J W250 5 QT I 7 gig; /0 nun/o /g COMPUTER /i SW/ICHER/v //V7'ERFACE M c U l 6665 sw fcyggs Z2 5 /2 ,4 VIDEO OURCE SOURC E CSOUR C56 7 E RM/MQLS t /7 CONTROL SYSTEM FOR AUDIO-VISUAL DEVICESCONNECTED BY CABLES BACKGROUND OF THE INVENTION capable of replayingpreviously recorded information in presently usable form, e.g., tapeplayback of audio and/or visual signals, or any apparatus capable ofgenerating information in presently usable form which information may becurrently used and/or recorded,

e.g., video camera and/or microphone. Hereafter such apparatus will bereferred to as A/V" equipment, apparatus, device or source. For example,in a modern school environment, it is often desirable to allow studentsto have remote access to tape recordings of a variety of lessons, or toview slides or motion picture presentations via video relay, or thelike. In libraries, it may be desirable to provide access at variousremote stations to information recorded on magnetic tape at a variety ofsource locations. A number of similar or analogous systems are presentlybeing utilized in industry and it is projected that many more suchsystems will be utilized in the future.

The installation and utilization of such systems can be relativelysimple where only a few sources of information and a few remote stationsare involved. However, when hundreds of sources and hundreds of stationsare involved, installation can be very complex and very costly. Wherecompletely automatic control is desired, the extensive amount of cablerequired to interconnect the units is a large factor in the installationcost. Further, in conventional systems, generally only one remotestation operates at a time and when a particular A/V device is beingcontrolled by one station, the other stations merely receive a busysignal requiring them to re-initiate a request for control when the lineis not busy.

SUMMARY OF THE INVENTION The present invention provides a system fordigital data exchange which can be used to interconnect a very largenumber of remote stations to as many A/V sources such as tape recorders,live cameras, film and slide projectors etc., and can provide for remotecontrol of these sources. In accordance with the particular systemdescribed herein, upon to 1,000 remote stations can be linked to up to1,000 A/V devices. Importantly, all of the remote stations are linked bymeans of a cable which is common to the station and all the devices arelinked by a cable which is common to the devices. Connectors, which canbe in the form of circuit boards, can be utilized to form groups of thesources and to form groups of the stations, the connectors being coupledto the cable. A master control unit accepts incoming command signalsfrom the remote stations and processes 2. them for transmission of theappropriate A/V device. Additionally, status information from controlledA/V devices are transmitted over the same cable back to displayindicators at the remote stations. As a result of the structuringconcepts herein, a building block" approach can be utilized to expandthe capacity of the system wherein additional devices and stations canbe readily accommodated. Further, the system provided herein utilizes acommand structure whichallows a remote station to signal for control ofa presently controlled device and remain on signal" while waiting forthe initial control to berelinquished. In this respect, the mastercontrol unit is structured to query all of the stations separately andsequentially to determine whether a command has been stored at thestation for transmission to the relinquished device. These functions arecarried out over the same cable and connectors linking the components.

With respect to specific operation of the system, there is provided:means operatively associated with each of the A/V devices forregistering an address unique to that device; means operativelyassociated with each of the remote stations for generating a signalrepresentative of a device address; means for transferring generatedsignals between the stations and the devices; means for comparing agenerated device address signal with a registered device address; andmeans for effecting a desired change upon identity between the signaldevice address and the registered device address.

Signals are generated in binary code decimals, as are other controlfunctions, and the cable comprises as many separate electricalconductors as the total number of decimals generated. A signal isgenerated by the remote station which is representative of that stations address and master control means are provided for receiving boththe station address signal and the device address signal for connectingthat station to the device to enable that station to receive informationcontaining signals from that device, e.g., by telemetric connection.Feedback signals are generated by the controlled device to indicate itsstatus to the control station and other remote stations and to indicatethe nature of the function of the device, if required, all over the samecommon cables and by means of comparison of generated signal addressesto registered signal addresses. In a particular mode of operation, acontrolling station can relinquish control of a particular device bygenerating a signal representative thereof. A feedback signal is thengenerated by the controlled device which is representative of suchrelinquishment and which communicates this information to all remotestations monitoring that device so that any such remote station canthereafter take control. In further embodiments, a supervisory remotecontrol station is provided having means for overriding the control ofany other station and having means for effecting the control of any ofthe devices by any of the other stations.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagramatic representationof a control system incorporating the present invention;

FIGS. 2, 3 and 4 are schematic diagrams expanding portions of thecontrol system of FIG. 1;

FIG. 5 is a diagramatic representation of details of a control unitportion of the control system of FIG. 1;

FIG. 6 is a diagramatic representation of details of station units ofthe control system of FIG. 1;

FIG. 7 is a diagramatic representation of details of a terminalconnected in FIG. 6;

FIG. 8 is a diagramatic representation of a manner of connecting theterminal of FIG. 7 to the station unit in FIG. 6;

FIG. 9 is a diagramatic representation of a particular station;

FIG. 10 is a diagramatic representation of source control units of thecontrol system of FIG. 1;

FIG. 11 is a diagramatic representation of a terminal unit utilized withthe source controllers of FIG. 8;

FIG. 12 is a diagramatic representation of a particular sourcecontroller; and

FIG. 13 is a diagramatic representation of a supervisor control stationutilized in the control system.

DETAILED DESCRIPTION Overall System A remote accessible A/V system maybe viewed as four separate grids:

1. Video 2. Audio 3. Device Control 4. Device Status Tallies For closedcircuit systems, these four grids may be combined into one. That is, anoperator is interested in the audio, video and control of only onedevice at any one time. Therefore, the data relative to device selection(i.e., relating a given operator station to a given device) issufficient to route function control signals from the station to thedevice, and to route device status information from the device back tothe station as well as providing the audio and video signals to thestation.

Irrespective of the total number of stations and devices, any stationmust appear to its operator as if it were the only station in thesystem. This means that for all intents and purposes, a selected devicemust behave as if it were located at the operator station. In addition,the system must never be busy for any operator. The activity at any onestation must be completely indepen dent of and have no effect on theactivity at any other station.

The means of selecting and controlling a device must be simple andrapid. Device status tallies must be displayed at the station in anunambiguous and clear manner. Such considerations as color versus blackand white video; sterephonic versus monophonic audio; and the widevariety of source devices (types as well as manufacturers) and monitorsmust not in any way hamper or proscribe the manner in which control andselection data are processed. By the same token, the system grids mustnot in any way determine the devices or monitors to be used. In otherwords, the random access and control system must be able to perform itsfunctions irrespective of the actual A/V environment of the totalsystem.

A further constraint is that the control system must be trulyexpandable. Expandable in this sense means that only the addition ofequipment is necessary for a growing system. Therefore, expansion mustbe accomplished simply by plugging additional units into the existingsystem in the same manner as new Christmas tree lights are added to anexisting string. At no time must expansion require the removal,modification or reworking of existing equipment.

Because of the impact of modern day computers, the access system must becomputer compatible. This requires that the data exchange must be indigital format. Provisions must be included in the basic systemframework for appropriate buffers for computer interface, both forinserting data into or extracting data out of the system. Both of theserequirements must also be met on a manual basis. The system must includeprovisions for manually activated supervisory stations which can bothenter or monitor data on a one at a time basis. Also means for theaddition at any time of automatic tally and status displays must beprovided.

The control system of the present invention may be viewed as a fixedprogram digital computer. Reference is now made to FIG. 1. The heart ofthe system is the master control unit 10 (hereinafter referred to as theMCU)..Three data busses are terminated at the MCU:

1. Station Buss ll 2. A/V Switcher Buss l2 3. Source Buss 13 The stationbuss 11 is a six twisted pair cable, which daisy-chains from the MCUthrough the various station terminal chassis 14. Each station terminalchassis accommodates ten remote operator stations. Each chassis has twoconnectors for daisy-chaining the buss, so that as additional chassisare incorporated into an existing system by plugging into the end of thestation buss. The system can accommodate up to of these chassis.

The source buss 13 is similar to the station buss, a six twisted paircable, daisy-chaining from the MCU through various source terminalchassis 16. Each chassis accommodates ten remotely controllable sources17. Expansion is identical to the stations. Again the system canaccommodate up to one hundred of these chassis.

The A/V switcher buss 14 is a ten twisted pair cable which daisy-chainsthrough the A/V switcher chassis I8. This cable carries the control datafor setting crosspoints. Each A/V switcher chassis 18 has ten inputs 19and twenty outputs 21, audio and video. These chassis allow forexpansion in both directions. For example, two chassis can providetwenty inputs by twenty outputs or ten inputs by 40 outputs. Thus, assystem requirements change, the A/V switcher network can also beexpanded incrementally. Irrespective of grid size, the A/V switcher buss12 is still only a ten twisted pair cable daisy-chaining from chassis tochassis. The system can accommodate A/V switcher chassis up to itsmaximum configuration, one thousand inputs by one thousand outputs.

The MCU 10 is a central polling device. In turn, up to one thousandstations are scanned. As a station is scanned, all data relative to thatstations status are transmitted over the station buss 11. These data arereceived and retransmitted over both the A/V switcher buss l2 and thesource buss 13 by the MCU 10. The station operator merely enters, via adecimal keyboard,

a three digit number corresponding to a desired source. After the digitshave been entered a transmit button is pressed to put the stationon-line". Until the station has been put on-line, its associatedterminal does not transmit when it is polled. Once on-line, the terminaltransmits the station status and desired device number each time it isscanned. In addition, if the operator is pressing a function button,this is also transmitted as long as the button is held in.

After the MCU has polled the stations, it polls up to one thousandsources. As each source is polled, its associated terminal transmits,via the source buss 13, its current status. These data include actualmachine status (i.e., run, stop, forward, reverse, etc.) and the addressof the controlling station. The MCU 10 receives the data and retransmitsit over the station buss 11. All stations which are on-line, examine thedata, and when a response from that source to which the station isaddressed appears, the station terminal stores the associated sourcestatus word. The stored data energize the proper illuminated functionpush but ton at the remote operator station 15.

It is possible that more than one station requests a particular source.The source terminal assigns control to the first station addressing it.This causes an AC- TIVE" indicator to be illuminated at the controllingstation. Subsequent stations selecting the source are placed in amonitor only status. This causes a MONI- TOR indicator to be illuminatedat these stations. At all stations addressed to a particular source, thesource status is displayed, but only functional commands originating atthe controlling station will be obeyed by the source. Should thecontrolling station go off-line by pressing the cancel push button,control available is indicated to all monitoring stations, by blinkingthe MONITOR indicator. The first station to press the transmitpush-button is then assigned control of the ad dressed source and allother stations automatically return to the MONITOR status. If allstations addressed to a source cancel, the source coupler automaticallygoes into a park cycle. This can be a stop, a rewind, or any desiredfunction as determined by user requirements.

The MCU 10 contains a supervisory station. This station can assign otherstations to sources, delegate control of the source as required, or takecontrol of a source itself. In addition, it can display the status ofany station or any source on a one-at-a-time, manually selected basis.

The total system scan time (complete station and source scans) is 320milliseconds irrespective of system size. The use of station terminalsas keyboard buffers, allows data entries to be made at a station withoutinterferring with any part of the system.

The use of common data busses allows the incorporation of computerinterfaces 22 and large scale system status boards as needs require.Since all system data appear on the station and source busses every 320milliseconds, the system in effect, updates itself three times a second.Very often however, the data are unchanging over long periods of time.To provide builtin data compression for future integration into acomputer system, every transmission from a station is tagged as towhether the data contained therein is in any way different from the lasttransmission from that station. This acts as a flag so that the computeris only alerted to data changes.

The function push-buttons at the stations, generate digital codes whenpressed. These codes are interpreted by the source terminals to bemachine functions. Only four machine functions are defined for remotestations:

1. Run

2. Stop 3. Forward 4. Reverse These four functions handle all thenecessary machine modes for retrieval of information. The system,however, allows for fifteen'functions. The eleven unused functions canbe implemented in any manner. For example, five functions (A,B,C,D,E)could be used for multiple choice testing. Two functions could be usedfor true/false testing. Again, since all data are present on the busses,test scoring can be implemented into the system.

The system is in effect non-existent to an operator. At no time is thesystem busy or overloaded. As far as the operator is concerned,.hesimply pushes buttons and gets immediate response. With this approachthe system of the present invention can be the basic grid for amultiplicity of uses.

Referring now to FIG. 2 there is shown more in detail the stationterminals and the manner in which they are connected into the system.The MCU 10 is connected by the station buss 11 to the station terminalswhich, as shown, may include a plurality of such terminals 25, 26, 27 upto thereof. A plurality of remote control stations, in this case 10stations, as shown generally at 28, 29 and 31, are connected to each ofthe station terminals 25, 26 and 27 respectively, in a mannerhereinafter described so that up to 1,000 remote control stations can beprovided in operative association with the station buss 11. Each of theremote stations is provided with a keyboard (not shown) for controlpurposes as will become clear hereinafter. As is shown at 11a, 11b and11c, the station buss 11 is daisy-chained to each of the stationterminals 25, 26 and 27. Also, if required, there may be provided astation status display apparatus 32 operative connected by a cable 33 tothe station buss 11 to provide an indication of the operative status ofany chosen remote station.

As is shown in FIG. 3, the MCU 10 is similarly connected by the sourcebuss 13 to the source terminals 16 which, as shown, may include aplurality of source terminals 35, 36 and 37 up to 100 thereof. Aplurality of sources, in this case 10, as shown generally at 38, 39 and41 are connected to each source terminal 35, 36 and 37, respectively. Insuch manner, up to 1,000 sources can be provided. As is shown, thesource buss 13 is daisy-chained at 13a, 13b and 13c to source terminals35, 36 and 37. If desired, a source status display 42 may be provided toshow the status of operation of any given source.

The system also includes a supervisor control unit for generating anoverriding signal, or for assigning a particular station to a particularsource, and may be connected as in the manner of a remote station, aswill be further described hereinafter. An A/V switcher 24 is alsoprovided for effecting connection between a station and a device, inthis case, by means of telemetry.

Referring now to FIG. 4, the MCU 10 is shown connected by the A/Vswitcher buss 12 to a plurality of A/V switchers 18 which, as shown, mayinclude a plurality of A/V switchers, in this case 6 such A/V switchers45 through 50, respectively. The A/V switcher buss 12, which is used forcontrol purposes, is daisy-chained as shown at 1211 through 12a through12e to A/V switchers 45 through 50, respectively. Each of the A/Vswitchers is capable of receiving ten different input signals, one fromeach of ten sources. Thus, ten signals may appear on buss 51 from tensources as schematically indicated at 52, and be applied as inputsignals to A/V switchers 45, 46 and 47 by the daisychained connectionshown at 51a and 511). Each of the A/V switchers has twenty A/V outputsas indicated at 53, each of which may be connected to any given remotestation. Thus, A/V switcher 45 may have up to 10 input signals connectedto twenty remote stations. By adding A/V switchers 46 and 47 as shown,forty more remote stations may receive the ten signals from ten sources.The number of A/V switchers may be expanded as at 510 to provide outputsas desired for the number of stations in the system.

if additional sources are employed so that more than ten inputs areprovided, then additional A/V switchers may be added as at 48, 49 and 50each of which receives 10 signals over the buss 61 from the ten sources62. The buss 61 is connected as before as shown at 610 and 61b and maybe expanded as at 610. Each of the twenty outputs 63 from A/V switchers48, 49 and 50 is connected to its corresponding output in A/V switchers47, 46 and 45 respectively over cables 64, 65 and 66 respectively. Thus,each one of 60 remote stations is now capable of receiving anyone oftwenty signals generated by twenty different A/V sources. It should nowbecome clear that additional A/V switchers may be deed as desired forany system to receive signals from any desired number of sources anddirect them to any desired number of remote stations.

In general operation, control signals are manually inserted through akeyboard into the individual remote stations to await instructions fromthe MCU 10 to transmit. The MCU 10 generates a signal which in effectsequentially addresses the stations and instructs an addressed stationto transmit its stored information over the station buss 11. The MCUmonitors this information and it is transmitted over the source buss 13to the source terminals. By appropriate comparison of the source addresscontained in the generated signal with the address of the sourcesassociated with a particular source terminal, control is effected ofthat source by the generating remote station.

The information which is generated by the station includes a sourceaddress and appropriate function commands or the like which areregistered in the MCU l and thereupon a signal is generated to theappropriate A/V switcher to transfer information from the source to thatstation. The MCU 10 is a digital data processor and is capable ofprocessing 1,000 remote stations and 1,000 A/V sources so as to generate1,000,000 switch points 1,000 stations I000 sources).

Master Control Unit Considering the system in greater detail, and withadditional reference to FIG. 5, the station buss 11 includes a sheath 71encasing 6 twisted pair of electrical conducting wires to form a 6signal conductor cable. The MCU 10 includes an oscillator 72, a programcounter 73, a data generator 74, a demodulator and a station and sourceaddress register 76. The program counter 73 generates signals to effectgeneration of other signals by other components to the MCU, of thestations and/or of the source terminals. The data generator 74 generatesinformation identifying and addressing particular stations. Theoscillator 72 generates a strobe or clock signal which is utilized tocause each of the stations and/or sources to respond at the same timeand at a predetermined period of time such that there is no interferencewith the program counter and data generator signals. The output from theMCU 10 consists of four signals from the data generator, each signal inbinary code decimal format, a strobe signal and a synchronizing signal(which is transmitted once during each cycle of the program counter tosynchronize the entire system as is well known in the art). Thisinformation is fed as shown, on the six conducting wires of the buss11-13 to the station terminals and source terminals, and from there tothe stations and sources.

Station Identification and Transmittal The MCU 10 monitors the line toprevent two stations transmitting simultaneously. Identification of astation and command to transmit is accomplished by sequentiallyaddressing each station in accordance with the program as set forth inTABLE 1.

Referring to TABLE 1, at each step wherein the program counter and datasignals are changed, a strobe signal is generated so as to effect timedresponse as hereinabove indicated. When the program counter and datasignals are both in their zero position a scanning mode is initiated.Thereafter as the program counter steps through its binary codedecimals, the stations are sequentially addressed by having the datasignals generated in the order shown, that is, first the hundreds digitthen the tens digit and then the units digit are generated in binarycode decimals. These signals are fed along the station buss 11 to all ofthe station terminals 14 and a particular remote station is identified.For example, as illustrated in TABLE I, when the program counter step isat l, then the signal from the data generator identifies the 100s unitof the particular station to be addressed. When the program counter stepis at 2, the data signal identifies the 's unit of the station to beaddressed, and in like manner the units digit is identified upon theprogram counter step being at 3. After the station has thus beenidentified, that station will be caused to transmit certain of itsinformation, as hereinafter described, and all of the sources will becaused to receive the signal thus transmitted assuming that the stationwhich has been addressed does in fact have information to transmit. Thistransmission is indicated in TABLE I wherein as the program countersteps through position 4 the status of the station addressed istransmitted by that station, i.e., ACTIVE, MONITOR, ON LINE, FUNCTION orCOMMAND CHANGE. When the program counter is at step 5, the desiredcommand is transmitted by the addressed station, i.e., transmit orcancel. When the program counter goes through steps 6, 7 and 8, theaddressed station transmits the address of a source it desires tocontrol by transmitting the 100's digit the 10's digit, and the unitssdigit of that address, respectively. As the program counter goes throughits next step a function code is transmitted, i.e., RUN, STOP, FORWARD,REVERSE, if in fact such exists for the particular source beingaddressed. If the source has no such function, then zeros aretransmitted to so indicate. As the program counter goes through stepsl2, l3 and 14 the station address is repeated by the MCU for use by thesource terminals. At step 15 a command may be received from the computer(if one is connected) to cause the entire sequence of signals to berepeated.

After the foregoing stage of transmission and reception has occurred,the entire process is repeated for the next sequential station, and soon until all 1,000 stations have thus been identified and have had anopportunity to transmit.

Referring now to FIGS. 6, 7 and 8, the manner in which the stations areassociated with their terminals 14 and the manner in which they receiveand transmit signals are shown. With specific reference to FIG. 6, eachstation 82 has a keyboard 81 or 81a which feeds information to betransmitted into a register 83. The output of each register is fed ontoa common buss 84 for transmittal over a line 85 (see FIG. 7) to thestation buss 11. In order to minimize wiring, a looping connectionsystem is utilized throughout, wherein drivers 54 and receivers 56 areconnected in parallel to the buss l1, and such components are utilizedwhere appropriate, although not specifically illustrated in the drawing.

The output from the register 83 is fed through an appropriate logicelement, such as a nand element 86, on signal from the station terminal25. Thus, the information which is transmitted by the station bymanipulation of the keyboard 81 is stored in the register 83 for furthertransmission. When the MCU applies a particular station addressidentifying a given station its respective station terminal, anadditional output is then transmitted to the nand logic element causingit to transmit the information stored on the particular register of thestation which has been identified, onto a common buss 84, into theterminal 25 and from there onto the station buss 11 via the connectingline 85.

Referring specifically to FIG. '7, the station address generated as adata signal (TABLE I) is applied through a demodulator 91 to a stationaddress comparator 92 in each of the station "terminals. If the hundredsand tens units of the station address is transmitted compares with thehundreds and tens units of the stations associated with the terminal,then the units code as transmitted is applied to the eight transmissionlines shown at 93. Each of the stations which are operatively associatedwith the station terminal 25 are each individually connected to four ofthe eight lines 93 in binary code fashion so that only that stationwhich is addressed by the units code will respond.

The manner of such connection is illustrated in FIG. 8 wherein it isseen that each of'the lines represents an 0 or a 1 binary code decimal.The units signal is applied to the lines in accordance with its binarycode decimal equivalent so as to generate a logically true signal overfour of the lines. That station which receives a logically true signalover each of its four connecting lines is the station being addressed bythe signal. Remote Control Station As described above, in response tobeing addressed, as the program counter steps through its next eightpositions the station transmits a signal in binary code fashion of thedevice it wishes to control along with a function and program signal.Referring to FIG. 9, each remote control station 82 is equipped with a12 button telephone-style keyboard 81 which allows the operator toaddress any of the source and control functions available in the system.A variety of capabilities can be provided ranging from simple numericselection of a source to detailed control of a source and of asequential tape search mode. The particular remote control station 82depicted in FIG. 9 provides for the numeric selection and subsequentoperator control of one of a possible 1,000 A/V sources and can entertape search data to digitally locate particular tape recorded programs.

In particular, five illuminable control status indicator switches101-105 are provided and labeled, respectively, active, stop, fastforward", reverse and show. The control status is displayed uponselecting a source. If control is available, an active indicator lightsup indicating that control has been automatically delegated to thestation. Should the station be assigned a monitor mode as a result ofsome other station being in control, the active indicator 101 will notbe illuminated, but rather a monitor indicator 106 will be illuminated.Upon the relinquishment of control by such other station, the monitor"indicator light 106 will blink. The first station to have its transmitswitch depressed will establish control and that active light willbecome illuminated while the other viewing stations will have theirmonitor indicators illuminated. Control may also be assigned to astation or taken away by a supervisory control station in the system ashereinafter described and will be displayed accordingly by the active ormonitor indicator lights.

The stop, forward", reverse and show switches l02-105 are utilized for asearch mode operation on an audio or video recorder as contro-led by atape search and source controller such as that indicated at 70 in FIG.10. During the search mode the forward or reverse indicator lights areon to indicate thedirection of search. At the completion of the searchsequence, the source goes into a play mode and the show indicator 105 isilluminated. The monitor" indicator 106 is illuminated when the selectedsource is not available for search; however, an A/V switch isaccomplished via the A/V switcher to place the station in a monitormode. Source Control Referring to FIG. 10, eachof the devices or sourcesof information, such as a tape recorder 111, motion picture filmprojector 112, 35 mm slide projector 113, or other audio and/or visualdevice, is connected to an individual controller for that source. Thecontrol may include tape search and programming functionings asillustrated by the tape search and source controller 70 or may be ofsimpler construction for utilization with unprogrammed devices such asthe ones illustrated by the source controllers 114, 115 and 116. Eachsource controller 70, 114, 115 or 116 accepts control commands from asource terminal 35 which is common to a plurality of the sourcecontrollers, as illustrated in P16. 8.

Referring to FIG. 11, the source address generated as a data signal(TABLE 1) is applied through a demodulator 121 to a source addresscomparator 122 in each of the source terminals such as 35. lf the sourceaddress as transmitted compares insofar as the 100s and 10 s units withthe 100 s and 10 s units of the sources associated with that terminal,then the units code as transmitted is decoded through the demodulator121 and applied to the eight transmission lines shown at 123. Each ofthe sources which are operatively associated with the terminal 16 viaits source controller are each individually connected to four of thetransmission lines 123 in binary code fashion, in the same manner asdescribed with respect to the connection of the stations to thetransmission lines 93 of the station terminal 25, as illustrated in FIG.7. The particular source which is addressed and only that source willrespond. In the event that that particular source is not at the momentbeing controlled, it will provide a signal to indicate its lack ofcontrol. This can be accomplished by a flip-flop circuit at the sourcecontroller having a l and state. If the flip-flop is in the 0" state,this indicates that the source being addressed is not being controlledand is free to be controlled by the addressing station. 1f the flip-flopis in the l condition, and the station active indicator is on, then thefunction is transferred over the line 127 to a relay interface 128 atthe source controller for utilization with the particular device beingused as the source. In the event that the source controller and thesource associated therewith are such that a search mode would berequired or desirable for that particular source, then the programaddress relating to the searching concept would be similarlytransferred. in the event that the source controller indicates that itis uncontrolled, i.e., the flip-flop is in the 0" condition, then whenthe comparator enable signal is generated, the address of the stationwhich is stored in the register 124 at the terminal is transferred overthe line 126 to the source controller station register 127.

In the source being utilized, such as a tape recorder, a televisiontuner, a camera or the like, a signal is developed in response to aparticular function control such as forward, reverse, stop, show, or thelike. In the event that a particular function has been ordered, a signalcan be developed by the device going into that mode of operation whichcan be transmitted back to the stations. Thus, the station address ascontained in the register 124 at the source controller and the statusinformation contained thereat in the status register 129 are transmittedvia the lines 131 and 132, respectively, and 133 along the buss ll-l3 tothe stations in the manner as will be indicated hereinafter with respectto scanning operation. A signal is thereby activated at the station thatthe particular source equipment is in the desired mode of operation,thus providing a check for the operator of that station that the sourcehas responded properly to the function as commanded by the stationoperator. If such a closed loop is not desired in a particular system,this feature of retransmittal of the command can be eliminated.

1f the flip-flop is in the l condition and the station monitor"indicator is lighted thereby indicating control by a different station,no further action by the source controller takes place with regard tothe information in the source terminal registers 123 and 124. DeviceScanning It is desirable to indicate to each of the stations the statusof a particular device at any given point in time so as to signal to thecontrolling station and the monitoring station or stations a change instatus of the device or source. A signal from the master control unit 10is utilized for scanning the devices at a point in time when the mastercontrol unit 10 has stepped through all the stations. As that point, themaster control unit will generate signals as set forth in TABLE 2.

Referring to TABLE 2, the first data signal generated in this scan modeis an invalid number such as 1111 to indicate that the mode is in fact ascan mode. Subsequently, the hundreds, tens and units in binary codedecimals of the source address is generated by the MCU 10 as was donewith respect to the stations address as previously described inconjunction with TABLE 1. When this occurs, and referring to FIG. 7, thedevice address is stored in a register 141 at the station terminal 25and applied to the comparator 92 at the station terminal in a mannersimilar to that previously described with respect to station scan.

The addressed source is caused to transmit. During the program steps 6,7 and 8 the MCU retransmits the source address transmitted during steps1, 2 and 3. This source address is compared to the stored source address at every remote station. Upon coincidence between stored andtransmitted source addresses a source match flip-flop is set at theremote station. At the step 11 program counter the status of the sourcewhich has been addressed is transmitted. The source match flip-flopbeing in a true state causes the source status data to be transferred tothat particular station, thus causing a given indicator to light up atthat station indicating the status of the device. For example, andreferring to FIG. 9, an appropriate indicating lamp such as the stop102, forward" 103, reverse 104, or show 105 lamp will be illuminated asdetermined by the status signal to indicate the status of the particularsource.

During the steps l2, l3 and 14 of the program counter the source whichis addressed is permitted to transmit the address of the station whichis controlling it. As the address of the controlling station compares tothe address of a particular station, then a signal is generated whichlights an appropriate indicator at the station. In this particularsystem, and referring again to FIG. 9, such an indicator is the lamp 101marked active. In the event that the station addresses do not comparewhile the source addresses do compare, the active lamp 101 will not beilluminated, but another appropriate indicating lamp 106 indicatingmonitor will be illuminated along with the particular function lamp102105 as above, to indicate that the source is not available forcontrol by this particular station, but that the station can monitor asignal from the source and hear and/or view it if such is desired.

Change of Control Referring now to the situation which occurs when astation relinquishes control or monitoring of a particular source. Ifthe station is merely a monitoring station and is non-controllingnothing will change in that particular source or source controller. Themessage of ter* mination being transmitted by that station will bereceived by the source controller in the manner previ ously described.The station address contained in that message of termination will becompared to the station address in the source controller register 127(FIG. 12) and, since the addresses will be different, no further actionby the source controller will take place. However, the MCU 10 willsignal the appropriate video switcher to terminate transmission ofinformation from the source previously monitored. On the other hand, ifthe station transmitting the termination message has a sta tion addresswhich compares with that stored in the source controller register 127,the following sequence of events will occur. First of all, the functionof the source 150 will not change since other stations may be viewingthe source although they are not controlling. However, the flip-flop isreset from its one to its state. This resetting causes the stationaddress appearing in the source controller shift register 127 to beautomatically set to an invalid number, that is, a number which cannotactually occur through utilization of the digits 0 through 9. The entiresignal now stored in the source controller serial shift registerincluding the invalid station address, is transmitted back to all of thestations. At each station a comparison is made as before so that if thesource address is the same as registered at that station, then a lamp isactivated which indicates the particular function contained in the transmitted message. However, as noted above, another comparison is made withthe stored station address. Since the station address transmitted withthe message is now invalid, it will indicate a non-coincidence with thestation addressed stored in each of the stations. In the previousdescription herein such non-coincidence was indicated by theillumination of a monitor lamp 106. However, in this particularinstance, a further comparison is made wherein it will be indicated thatthe station address contained in the transmitted message is composed ofan invalid number, e.g., entirely of ones. When this occurs, the monitorlamp 106 will blink. This provides information to the operators of thestations which have been non-controlling, that if that station wishes togain control of this particular source, all that is required is that thetransmit" button be pushed. This will in turn cause the transmission ofa signal from that station to all of the source controllers, asdescribed above. Accordingly, the sequence of events as above describedwill occur with the station having its transmit button 100 first pushedand that station address will be transmitted to the source controllerregister 127 and the flip-flop transferred from the 0 to the l" state,thus causing that particular station to now have control. SupervisorControl Station Referring to FIG. 13, a supervisor control station isillustrated. This station can be utilized simply as a monitor station oras a remote control station similar to that indicated at 82, it canselect to display a station status, a source status, or it can beutilized to override the control by any station in the system, or candelegate control to any station in the system. The supervisor controlstation 160 also has a telephone-style keyboard 81a whereby it canserially enter an eight digit number. When utilized in a monitor modeonly, the first three digits are the address of the supervisor controlstation, the next three digits are the desired source address and thelast two digits are the desired program number at the source (if thesource is not equipped with a search unit, only a six digit number isentered). After data are entered a transmit button 161 is depressed tosend the data to the MCU 10 over the station buss 1 l. A cancel button162 is provided which upon depression thereof takes the supervisorcontrol station 160 offline" or corrects a data entry. An eight digitnixie display 163 is provided to indicate the address of the remotestation, the source and the program as appropriate.

In the delegation mode, an eight digit number is also entered onto thekeyboard. The first three digits are the address of a remote stationselected for delegation. The next three digits are the address of thedesired source. The last two digits are the desired program number atthe source if the source is, equipped with a search unit. After data areentered, the transmit button 161 is depressed to send the data to theMCU 10 to thus route the source data to the addressed remote station.This operation may be repeated until all desired sta tion/sourceconnections are made. To delegate source control to a station an active"button 164 rather than the transmit" button 161 is depressed after dataare entered. Status indicators l65-168, corresponding to those of thestations, provide a display of whichever station the supervisor controlstation is addressing. To accomplish the delegation mode, the supervisorcontrol station transmission message contains an appropriate signalwhich is received by all of the stations, but acted upon only by thatstation having a station address identical to the station address astransmitted by the supervisor control station. The addressed stationacts upon the information to replace the source address in its register83 (FIG. 6) with the source address contained in the transmitted messagefrom the supervisor control station.

, In the override mode, again an eight digit number is entered. Thefirst three digits are the address of the supervisor control station160. The next three digits are the desired source address. The last twodigits are the desired program number at the source, if equipped with asearch unit. After the data are entered, the active push button 164 isdepressed causing the supervisor control station to obtain control ofthe source as well as to remove control from whichever stationpreviously had control. However, all stations previously receivinginformation from the source remain in a monitor mode. The activeindicator 164 at the supervisor control station 160 will be illuminatedas well as whichever in- I dicator corresponds to the current status ofthe source; the function control push buttons 165-168 are activated toallow the supervisor control station 160 to control the source. Themessage transmitted by the supervising control station is received inthe source controller station address register 127 and the statusregister 129. If a function mode is contained in the message, it willtotally override the station address appearing in the source controllerregister 127 and cause control to be assumed in accordance with thefunction code appearing in the message from the supervisor controlstation 160. When this occurs, the station addressed by the supervisorcontrol station 160 assumes control irrespective of the address of thestation appearing previously in the register 127. The supervisor controlstation can obtain such control by transmitting his own address as anoverriding station address.

An additional feature of this system, in the event that the stationcontrolling the source has commanded the source to a status differentfrom that which it presently occupies, the source will transmit back itspresent status and then as soon as the status of the source has changedto that commanded, an additional signal indicating the new status istransmitted back to all of the stations. During the interim while thesource is changing from its current status to the commanded status, thelines are open for additional utilization by any other station to anyother source. Such time sharing utiliza tion may be effected for anyfunction of the source which requires several seconds at a time such assearching or the like. To effectuate such time sharing, the present andchanges status signals are transmitted together with the device addressand station address to be received by the stations in the mannerindicated above.

Audio-Video Switcher Referring to the function of the A/V switcher, andreferring back to FIG. 4 and to the description of the MCU 10particularly with respect to its register 76, that register 76 isadapted to receive only the source address and the station address. Whenthe lOOs, 10s and units numbers of these two addresses are storedtherein, the register 76 is not capable of receiving any furtherinformation and a load pulse is generated which is applied to an A/Vswitch interface which indicates to receiving apparatus that the videoswitch can now be activated to accomplish the interconnection of theparticular source whose address is in the register 76 to the particularstation whose address is stored therein. The aforenoted load pulse maybe generated by a variety of methods. In a particular method, the MCU 10is adapted such that when the bits of information containing the stationaddress and device address have been received by the register 76, acounter therein (not shown) indicates this by moving through separateincrements. At this point, a signal is generated which causes theregister 76 to not receive additional information and. simultaneouslyalso causes a load pulse to be generated by equipment therefor (notshown). The structure of the components are such that after the stationhas utilized information, or if the information has not been utilized ina predetermined period of time, a signal is generated by the station soas to cause the switch to be deactivated insofar as that device-stationinterface is concerned.

As indicated in FIG. 4, the signals from each of the ten sources areconnected through an appropriate decoder to a common buss which would beconnected to an amplifier the output of which is one of the twentyoutputs. The station and source address signals then are used tointerconnect cross points thereby to apply the desired input signal tothe desired amplifier.

What is claimed is:

1. A system for control of any of a plurality of audiovisual sources byany of a plurality of remote stations, comprising:

a plurality of audio-visual sources; first cable means common to saidaudio-visual source;

first means connecting each of said audio-visual sources to said firstcable means;

a plurality of remote stations, each of which is individually operatorcontrolled; second cable means common to said remote stations;

second means connecting each of said remote stations to said secondcable means;

address storage means operatively associated with each of saidaudiovisual sources for storing an address unique to that audio-visualsource;

address generator means operatively associated with each of said remotestations for generating signals representative of an audio-visual sourceaddress;

signal transfer means connected to said common cables for transferringgenerated signals between said stations and said sources;

comparator means connected to each audio-visual source for comparing agenerated audio-visual source address signal with a stored audio-visualsource address; and

means for establishing control by that remote station over thataudio-visual source the address of which has been generated by said thatremote station when said that audio-visual source is not beingcontrolled by any other of said remote stations upon identity betweensaid generated signal audiovisual source address and said storedaudio-visual source address.

2. The system of claim 1 wherein said signal general ing means comprisesmeans for generating a binary code decimal signal of predeterminednumber of decimals, said cable comprising at least as many separateelectrical conductors as required to define one binary code decimaldigit.

3. The system of claim 1 including means for generating programmedsignals in first binary code decimals of predetermined number ofdecimals for commanding data to be transmitted and means for generatingdata signals in second binary code decimals of predetermined number ofdecimals in representation of data to be transmitted.

4. The system of claim 3 including means for generating a strobe signaltimed tosaid signal generation, and means at each of said stations andaudiovisual sources responsive to said strobe signal for timing responsethereto to said command or data signals.

5. The system of claim 1 including a plurality of station terminals eachstation terminal having means for electrically associating apredetermined plurality of said remote stations therewith and means foreffecting said second common cable connection.

6. The system of claim 5 including nand logic element for each stationoperatively connecting said station to its connector.

7. The system of claim 1 including a plurality of audio-visual sourceterminal connectors, each audiovisual source terminal having means forelectrically associating a predetermined plurality of said audio-visualsources therewith and means for effecting said first common cableconnection.

8. The system of claim 7 wherein each audio-visual source terminalincludes a plurality of connecting lines corresponding to a number ofbinary code decimals at least as great as required for selectiveconnection to each audio-visual source associated therewith, saidaudio-visual source being selectively connected to said connecting linesin binary code format.

9. The system of claim 1 including: means operatively associated witheach of said remote stations for generating a signal representative ofthat stations address; and

means for receiving said station address signal and said audio-visualsource address signal for connecting said station to said audio-visualsource for reception at said station of intelligence information fromsaid source.

10. The system of claim 1 including means for sequentially signalingeach of said plurality of stations to generate said signal.

11. The system of claim 1 including means operative ly associated withat least one of said stations for generating a signal representative ofa function desired to be performed by an addressed audio-visual sourceand means connected to said addressed audio-visual source operative uponidentity of said that remote station as having generated said functionsignal, for effecting a performance of said function.

12. The system of claim 1 including:

means operatively associated with at least one of said audio-visualsources for generating a status signal representative of theaudio-visual source address thereof and representative of a functionbeing performed thereby;

means operatively associated with at least one of said remote stationsfor registering the address of said associated audio-visual source; and

means for receiving said signal and comparing said associatedaudio-visual source address with said station-registered audio-visualsource address to effect upon identity thereof an indication of thenature of said function.

13. The system of claim 12 including means for sequentially signalingeach of said plurality of audiovisual sources to generate said statussignal.

14. The system of claim 1 including:

means operatively associated with at least a first remote station forgenerating a signal representative of that stations address fortransference to each of said audio-visual sources;

means operatively associated with said first station for storing saidfirst station address and said audiovisual source address;

means operative upon said identity for transferring a feedback signalrepresentative of said first station address and said audio-visualsource address to each of said remote stations; and

means operatively associated with said first station for comparing suchfeedback signal audio-visual source address with said first stationregistered audio-visual source address to effect upon identity thereofan indication of control of said source.

15. The system of claim 14 including:

means operatively associated with said first station for comparing saidfeedback signal station address with said stored first station addressto effect upon identity thereof an indication of control by said firststation and to effect upon non-identity thereof an indication of lack ofcontrol by said first station.

16. The system of claim 1 wherein a first station is in operativecontrol of a first audio-visual source, and including:

means operatively associated with said first station for generating asignal representative of relinquishment of said control; meansoperatively associated with said first audiovisual source for receivingsaid relinquishing signal and in response thereto generating a signalrepresentative of the address of said first audiovisual source and anadditional signal representative of non-control by any of said pluralityof said remote stations; means operatively associated with at least asecond of said remote stations for registering the address of said firstaudiovisual source and comparing said generated audio-visual sourceaddress thereto; and

means operatively associated with said second remote station forreceiving said additional signal and, upon identity between said firstaudio-visual source address and second station registered audio-visualsource address, effecting an indication of availability for control ofsaid first audiovisual source.

17. The system of claim 1 including:

means operatively associated with at least a first remote station forstoring said first station address;

means operatively associated with at least a second remote station forgenerating a signal representative of said first station address and asignal representative of the address of an audio-visual source desiredto be under the control of said first station; and

means for comparing said generated first station address with saidstored station address to effect upon identity thereof a registration ofsaid desired audio-visual source address in operative association withsaid first station.

18. The system of claim 17 including:

means operatively associated with said second remote station forgenerating a signal representative of a function desired to be performedby said desired audio-visual source; and

means for effecting upon said identity of said first station addresswith said stored station address, a registration of said desiredfunction in operative association with said desired audio-visual source.

19. The system of claim 1 further including switch means connectedbetween said audio-visual sources and said remote stations and means forcontrolling said switch means to connect the intelligence signal from anaddressed audio-visual source to a remote station addressing saidaddressed audio-visual source.

20. The system of claim 19 wherein said switch means includes sufficientinput terminals to receive intelligence signals from each of saidaudio-visual sources and has sufficient output terminals to provide anoutput terminal for each remote station.

1. A system for control of any of a plurality of audio-visual sources byany of a plurality of remote stations, comprising: a plurality ofaudio-visual sources; first cable means common to said audio-visualsource; first means connecting each of said audio-visual sources to saidfirst cable means; a plurality of remote stations, each of which isindividually operator controlled; second cable means common to saidremote stations; second means connecting each of said remote stations tosaid second cable means; address storage means operatively associatedwith each of said audio-visual sources for storing an address unique tothat audio-visual source; address generator means operatively associatedwith each of said remote stations for generating signals representativeof an audio-visual source address; signal transfer means connected tosaid common cables for transferring generated signals between saidstations and said sources; comparator means connected to eachaudio-visual source for comparing a generated audio-visual sourceaddress signal with a stored audio-visual source address; and means forestablishing control by that remote station over that audio-visualsource the address of which has been generated by said that remotestation when said that audio-visual source is not being controlled byany other of said remote stations upon identity between said generatedsignal audio-visual source address and said stored audio-visual sourceaddress.
 2. The system of claim 1 wherein said signal generating meanscomprises means for generating a binary code decimal signal ofpredetermined number of decimals, said cable comprising at least as manyseparate electrical conductors as required to define one binary codedecimal digit.
 3. The system of claim 1 including means for generatingprogrammed signals in first binary code decimals of predetermined numberof decimals for commanding data to be transmitted and means forgenerating data signals in second binary code decimals of predeterminednumber of decimals in representation of data to be transmitted.
 4. Thesystem of claim 3 including means for generating a strobe signal timedto said signal generation, and means at each of said stations andaudio-visual sources responsive to said strobe signal for timingresponse thereto to said command or data signals.
 5. The system of claim1 including a plurality of station terminals each station terminalhaving means for electrically associating a predetermined plurality ofsaid remote stations therewith and means for effecting said secondcommon cable connection.
 6. The system of claim 5 including nand logicelement for each station operatively connecting said station to itsconnector.
 7. The system of claim 1 including a plurality ofaudio-visual source terminal connectors, each audio-visual sourceterminal having means for electrically associating a predeterminedplurality of said audio-visual sources therewith and means for effectingsaid first common cable connection.
 8. The system of claim 7 whereineach audio-visual source terminal includes a plurality of connectinglines corresponding to a number of binary code decimals at least asgreat as required for selective connection to each audio-visual sourceassociated therewith, said audio-visual source being selectivelyconnected to said connecting lines in binary code format.
 9. The systemof claim 1 including: means operatively associated with each of saidremote stations for generating a signal representative of thatstation''s address; and means for receiving said station address signaland said audio-visual source address signal for connecting said stationto said audio-visual source for reception at said station ofintelligence information from said source.
 10. The system of claim 1including means for sequentially signaling each of said plurality ofstations to generate said signal.
 11. The system of claim 1 includingmeans operatively associated with at least one of said stations forgenerating a signal representative of a function desired to be performedby an addressed audio-visual source and means connected to saidaddressed audio-visual source operative upon identity of said thatremote station as having generated said function signal, for effecting aperformance of said function.
 12. The system of claim 1 including: meansoperatively associated with at least one of said audio-visual sourcesfor generating a status signal representative of the audio-visual sourceaddress thereof and representative of a function being performedthereby; means operatively associated with at least one of said remotestations for registering the address of said associated audio-visualsource; and means for receiving said signal and comparing saidassociated audio-visual source address with said station-registeredaudio-visual source address to effect upon identity thereof anindication of the nature of said function.
 13. The system of claim 12including means for sequentially signaling each of said plurality ofaudio-visual sources to generate said status signal.
 14. The system ofclaim 1 including: means operatively associated with at least A firstremote station for generating a signal representative of that station''saddress for transference to each of said audio-visual sources; meansoperatively associated with said first station for storing said firststation address and said audio-visual source address; means operativeupon said identity for transferring a feedback signal representative ofsaid first station address and said audio-visual source address to eachof said remote stations; and means operatively associated with saidfirst station for comparing such feedback signal audio-visual sourceaddress with said first station registered audio-visual source addressto effect upon identity thereof an indication of control of said source.15. The system of claim 14 including: means operatively associated withsaid first station for comparing said feedback signal station addresswith said stored first station address to effect upon identity thereofan indication of control by said first station and to effect uponnon-identity thereof an indication of lack of control by said firststation.
 16. The system of claim 1 wherein a first station is inoperative control of a first audio-visual source, and including: meansoperatively associated with said first station for generating a signalrepresentative of relinquishment of said control; means operativelyassociated with said first audio-visual source for receiving saidrelinquishing signal and in response thereto generating a signalrepresentative of the address of said first audio-visual source and anadditional signal representative of non-control by any of said pluralityof said remote stations; means operatively associated with at least asecond of said remote stations for registering the address of said firstaudio-visual source and comparing said generated audio-visual sourceaddress thereto; and means operatively associated with said secondremote station for receiving said additional signal and, upon identitybetween said first audio-visual source address and second stationregistered audio-visual source address, effecting an indication ofavailability for control of said first audio-visual source.
 17. Thesystem of claim 1 including: means operatively associated with at leasta first remote station for storing said first station address; meansoperatively associated with at least a second remote station forgenerating a signal representative of said first station address and asignal representative of the address of an audio-visual source desiredto be under the control of said first station; and means for comparingsaid generated first station address with said stored station address toeffect upon identity thereof a registration of said desired audio-visualsource address in operative association with said first station.
 18. Thesystem of claim 17 including: means operatively associated with saidsecond remote station for generating a signal representative of afunction desired to be performed by said desired audio-visual source;and means for effecting upon said identity of said first station addresswith said stored station address, a registration of said desiredfunction in operative association with said desired audio-visual source.19. The system of claim 1 further including switch means connectedbetween said audio-visual sources and said remote stations and means forcontrolling said switch means to connect the intelligence signal from anaddressed audio-visual source to a remote station addressing saidaddressed audio-visual source.
 20. The system of claim 19 wherein saidswitch means includes sufficient input terminals to receive intelligencesignals from each of said audio-visual sources and has sufficient outputterminals to provide an output terminal for each remote station.